The present invention relates to a method and device for fishing up an immersed body remotely from a position disposed substantially above this body.
More particularly, the invention applies to the recovery of an anchorage line, such as a chain for mooring sea vessels, such as oil platforms. The invention may in particular be applied to the field of oil effluent production, in Polar seas in regions subjected to the passage of icebergs, and in regions subjected to very severe weather conditions (wind of 150 km/hour, waves reaching 30 m); when it is a question of rapidly removing a surface vessel, such as a processing platform, from a critical zone. This vessel may moreover be coupled to a bottom base by flexible lines, as is described in the patent applications FR 2 600 710, FR 2 600 711 and FR 2 600 712.
Removal of the vessel takes place by leaving in position only the sea bottom installations and the anchorage lines for the vessel.
It is known, for locating or lifting a deadman disposed on the sea bed, to use a surface buoy connected by a link to this deadman and effect an upward pull on the link for lifting the deadman. This technique cannot be applied to the lifting of coil platform anchorage chains, for the existence of buoys and links in the vicinity of the anchorage chains during storms, when the platform is anchored to the sea bed (at least approximately 100 m below the level of the surface of the sea) risks tangling the links and chains together or fatiguing the elements subjected to the high stresses.
In order to overcome these drawbacks in particular, the invention provides a method and device which can be used for lifting deadmen and, in particular, anchorage chains for oil platforms disposed in subsea waters having difficult access.